SPARCstation 20 with SCSI2SD

[systems_glitch]

Nice work, indeed! The clearance issue is part of why I made the repair
module boards.

Thanks,
Jonathan

On Wed, Dec 5, 2018 at 9:54 AM Maciej W. Rozycki via cctalk <
cctalk at classiccmp.org> wrote:

> On Sun, 2 Dec 2018, Jeffrey S. Worley via cctalk wrote:
>
> > The re-work of that Dallas nvram chip is just beautiful.  It makes me
> > ashamed of myself.  (I just chopped into the epoxy with a pocket knife,
> > soldered two leads, and velcroed the new batteries somewhere inside the
> > machine I installed it in.)
>
>  There is very little clearance in DECstation 5000 systems, like .1", as
> per the TURBOchannel specification, between the top of the Dallas chip and
> the bottom of any TURBOchannel option placed right above it (some have
> components underneath, including large ICs), and I think the risk of
> breaking such a non-standard wiring while shuffling option cards is not to
> be ignored either.  Also the design of the system box makes it very
> difficult to choose a suitable location for a distant battery holder that
> would not obstruct anything.
>
>  So I decided to do that properly at the cost of it taking perhaps a
> little longer to rework a single chip.
>
>  NB a CR1220 cell is supposed to last for ~8 years in this application if
> running on battery power all the time, which I think is good enough.  A
> CR2032 cell would last ~50 years, which I think is an overkill, given that
> the seal is expected to fail much earlier, like after 10 years.
>
>  An encapsulated power module could instead be used such as the Renata
> 175-0, where space permits, which would indeed last some 50 years, being
> airtight, but I haven't seen any reports of its use in this application (I
> have a couple of those on DEC NVRAM boards and last time I checked they
> still had the power to hold 1MiB SRAM memory contents after 25+ years).
>
> > I salute you sir.
>
>  :)  So far I only made 2 of these, but more are in the pipeline (waiting
> for a free weekend).
>
>   Maciej
>